Ch 16.3 (Pg. 460-464):Darwin Presents His Case

Darwin and Alfred Russel Wallace- Alfred Russel Wallace was a

naturalist working in Malaysia, who also had similar ideas about evolution

- In 1858 Darwin and Wallace co-presented their theory to the Linnaean Society of London

- In 1859 Darwin published his book, On the Origin of Species

Darwin’s Case for Evolution- Struggle for Existence

- More individuals are produced than can survive, and must compete with each other

- Variation and Adaptation- Some variations are better suited

to the environment than others

- Inherited variations that increase an organism’s ability to survive and reproduce are adaptations

Darwin’s Case for Evolution- “Survival of the Fittest”

- Differences in adaptations affect an individual’s survival

- Organisms that are best adapted to their environment survive and reproduce better than others, and have the highest fitness

Darwin’s Case for Evolution

- Natural Selection- Occurs when:1. More individuals are born than

can survive2. There is natural heritable

variation3. There is unequal fitness

between individuals

Descent with Modification- Means that all organisms are

descended from a common ancestor- Many generations must pass on traits

with slight modifications to create new species